Fix inconsistencies in ROS resource keywords

[nahueespinosa]

Feature description

After adding basic ROS 2 orchestration support in the form of a Robot Framework support library in #54, we noticed a couple of issues with the keyword definition and collisions with ROS 1:

• Some keywords would do exactly the same thing in both versions and they were de-duplicated in a ros_common resource.
• Other keywords would need to do different things depending on the version and they were disambiguated by adding "ROS 2" to their name.

There are still some inconsistencies though, e.g. keywords that explicitly name ROS could be used for both ROS 1 and ROS 2. For example:

Uses ${launch_file} in ${package_name} ROS package as rig

There is also the idea of adding sugar on top to route to the right version.